A. Field of Invention
The present invention relates to a laser system having an optical fiber doped with Praseodymium (Pr.sup.3+). The laser system energizes the Pr.sup.3+ to produce a optical gain by the .sup.1 G -.sup.3 H.sub.5 transition at a wavelength in the range of about 1.25 to 1.34 microns. The optical fiber can be glass, crystalline, or a combination thereof, and made out of a halide or chalcogenide host or combinations thereof. The optical fiber can be energized by direct pumping of the Pr.sup.3+ or by indirect pumping, by using rare earths and other sensitizers as co-dopants located in a region of the optical fiber so that they can absorb pump energy and transfer excitation to the Pr.sup.3+. The optical fiber can be incorporated into an amplifier, an oscillator, or a superluminescence source. The output can be applied to communications, a gyroscope or other sensors, printing, and medical instruments.
B. Description of the Related Art
There is a need to amplify optical signals in many fields of technology. In fiber optic communications, for example, to send cable television signals to many households over optical fibers, it is necessary to split the signals into many receivers. Without amplification, one would in all practicality eventually run out of signal to divide. It is through amplification (increasing the strength of the signal) that such signals can be provided to many households. One way to amplify the light signals is to convert them to electrical signals, amplify the electrical signals, and then reconvert the electrical signals back to light again. This is a relatively complicated and expensive approach, but it is necessary where there is no known, practical device that can optically amplify the relevant region of the light spectrum.
For example, prior to this invention, it has been essentially necessary to use electrical rather than optical amplification for one of the primary wavelengths used in communications (1.25-1.34 microns). Further, in the search to find a way to optically amplify this wavelength region, despite great efforts, solutions have been elusive. Thus, when aspects of the present invention were made public, the Wall Street Journal reported them as a "breakthrough in optical signal amplification" (on Jun. 12, 1991, in an article titled "Big Cost Savings for Fiber-Optic Systems are seen in New Way to Amplify Signals").